ABSTRACT The photo-actuation behavior of nanocomposites based on ethylene–vinylacetate copolymer ... more ABSTRACT The photo-actuation behavior of nanocomposites based on ethylene–vinylacetate copolymer (EVA) and styrene–isoprene–styrene (SIS) block copolymer filled with well-dispersed and modified multiwalled carbon nanotubes (MWCNTs) is discussed in this paper. The nanocomposites were prepared by casting from solution. To improve the dispersion of the MWCNTs in EVA, the MWCNT surface was modified with a non-covalent surfactant, cholesteryl 1-pyrenecarboxylate (PyChol). To prepare SIS nanocomposites, the MWCNT surface was covalently modified with polystyrene chains. The good dispersion of the filler was confirmed by transmission electron microscopy (TEM). Special, custom-made punch/die molds were used to create a Braille element (BE)-like shape, which under shear forces induces a uniaxial orientation of the MWCNTs within the matrix. The uniaxial orientation of MWCNTs is an essential precondition to ensure the photo-actuating behavior of MWCNTs in polymeric matrices. The orientation of the MWCNTs within the matrices was examined by scanning electron microscopy (SEM). Nanocomposite BEs were illuminated from the bottom by a red light-emitting diode (LED), and the photo-actuation was investigated by confocal laser scanning microscopy (CLSM). When the BEs were exposed to light, a temporary increase in the height of the element was detected. This process was observed to be reversible: after switching off the light, the BEs returned to their original shape and height.
Abstract. The photo-actuating behavior of new polymeric nanocomposite materials based on a commer... more Abstract. The photo-actuating behavior of new polymeric nanocomposite materials based on a commercial elastomer, an ethylene-vinylacetate copolymer (EVA), filled with multiwalled carbon nanotubes (MWCNT) was investigated. A good dispersion of the MWCNT within the elastomeric matrix was ensured by using a novel, specific compatibilizer consisting of pyrenyl and cholesteryl groups. A uniaxial orientation of the MWCNT within the matrix was induced with shear forces by employing a special custom-made punch/die system. Good dispergation and alignment of the MWCNT within the matrix were demonstrated by scanning electron microscopy. Transmission electron microscopy showed a good dispersion of the MWCNT within the composite. Photo-actuation was qualitatively characterized by atomic force microscopy and quantitatively characterized by nanoindentation. The samples prepared in the form of Braille element showed expansion upon illumination by light diodes. The maximal height deformation changes about 15% was detected when a blue diode was used.
High-density polyethylene (HDPE)-based hybrid nanocomposites containing graphene nanoplatelets (G... more High-density polyethylene (HDPE)-based hybrid nanocomposites containing graphene nanoplatelets (GnPs) and multiwall carbon nanotubes (MWCNTs) were fabricated using melt mixing followed by compression molding. The influences of size and weight ratio of both carbon-based nanofillers on the electrical, thermal, and mechanical properties of hybrid nanocomposites were evaluated. This study proves that the size and weight ratio of carbon-based nanofillers play a critical role in determining these properties. The optimum size and weight ratio of GnPs and MWCNTs are determined at the maximum achieved enhancement for each property. The HDPE-based nanocomposites containing GnPs with larger surface area and MWCNTs with higher aspect ratio display the highest electrical conductivity at GnPs/MWCNTs weight ratio of 2/3. The combination of GnPs with larger surface area and MWCNTs with lower aspect ratio provides the maximum Young’s modulus enhancement of hybrid nanocomposites at 1/4 weight ratio of GnPs and MWCNTs. The nanocomposite containing GnPs with the largest lateral size and MWCNTs with a higher aspect ratio at a 3/2 weight ratio exhibits the highest thermal conductivity. Also, at around the percolation threshold of GnPs, the incorporation of MWCNTs with larger aspect ratio into the HDPE-based nanocomposites containing GnPs with the largest lateral size shows a distinct synergic effect on the thermal conductivity and Young’s modulus, while an additive effect on the electrical conductivity and thermal stability.
Photomechanical actuation is preferred to electromechanical transduction because of some advantag... more Photomechanical actuation is preferred to electromechanical transduction because of some advantages including wireless connection, a producing low noise, fast response etc. However, only few materials actually exhibit photoactuation. Recently, nanotube-enriched elastomeric polymers have shown photo-actuating properties; the best results were reported for liquid crystals elastomers. In the present paper we discuss photo-actuating behavior of new photoactuating materials based on the
The effects of the aspect ratio and the addition of multiwall carbon nanotubes (MWCNTs) on the mo... more The effects of the aspect ratio and the addition of multiwall carbon nanotubes (MWCNTs) on the morphological, electrical, mechanical and thermal properties of high-density polyethylene (HDPE)-based nanocomposites are investigated. The HDPE nanocomposites with various amounts up to 18.74 wt.% of MWCNTs that have two different aspect ratios (AR), (200–400(M58) and 500–3000(M12)) were prepared by a melt mixing method, followed by compression molding. The results demonstrate that the addition of MWCNTs enhances the electrical, mechanical and thermal properties of the HDPE/MWCNTs nanocomposites. The HDPE nanocomposites with higher aspect ratio MWCNTs demonstrated a slightly better enhancement in the morphological and electrical properties than the other ones with lower aspect ratio MWCNTs. Additionally, Young's modulus and the thermal stability increased with increasing aspect ratio of MWCNTs.
ABSTRACT The photo-actuation behavior of nanocomposites based on ethylene–vinylacetate copolymer ... more ABSTRACT The photo-actuation behavior of nanocomposites based on ethylene–vinylacetate copolymer (EVA) and styrene–isoprene–styrene (SIS) block copolymer filled with well-dispersed and modified multiwalled carbon nanotubes (MWCNTs) is discussed in this paper. The nanocomposites were prepared by casting from solution. To improve the dispersion of the MWCNTs in EVA, the MWCNT surface was modified with a non-covalent surfactant, cholesteryl 1-pyrenecarboxylate (PyChol). To prepare SIS nanocomposites, the MWCNT surface was covalently modified with polystyrene chains. The good dispersion of the filler was confirmed by transmission electron microscopy (TEM). Special, custom-made punch/die molds were used to create a Braille element (BE)-like shape, which under shear forces induces a uniaxial orientation of the MWCNTs within the matrix. The uniaxial orientation of MWCNTs is an essential precondition to ensure the photo-actuating behavior of MWCNTs in polymeric matrices. The orientation of the MWCNTs within the matrices was examined by scanning electron microscopy (SEM). Nanocomposite BEs were illuminated from the bottom by a red light-emitting diode (LED), and the photo-actuation was investigated by confocal laser scanning microscopy (CLSM). When the BEs were exposed to light, a temporary increase in the height of the element was detected. This process was observed to be reversible: after switching off the light, the BEs returned to their original shape and height.
Abstract. The photo-actuating behavior of new polymeric nanocomposite materials based on a commer... more Abstract. The photo-actuating behavior of new polymeric nanocomposite materials based on a commercial elastomer, an ethylene-vinylacetate copolymer (EVA), filled with multiwalled carbon nanotubes (MWCNT) was investigated. A good dispersion of the MWCNT within the elastomeric matrix was ensured by using a novel, specific compatibilizer consisting of pyrenyl and cholesteryl groups. A uniaxial orientation of the MWCNT within the matrix was induced with shear forces by employing a special custom-made punch/die system. Good dispergation and alignment of the MWCNT within the matrix were demonstrated by scanning electron microscopy. Transmission electron microscopy showed a good dispersion of the MWCNT within the composite. Photo-actuation was qualitatively characterized by atomic force microscopy and quantitatively characterized by nanoindentation. The samples prepared in the form of Braille element showed expansion upon illumination by light diodes. The maximal height deformation changes about 15% was detected when a blue diode was used.
High-density polyethylene (HDPE)-based hybrid nanocomposites containing graphene nanoplatelets (G... more High-density polyethylene (HDPE)-based hybrid nanocomposites containing graphene nanoplatelets (GnPs) and multiwall carbon nanotubes (MWCNTs) were fabricated using melt mixing followed by compression molding. The influences of size and weight ratio of both carbon-based nanofillers on the electrical, thermal, and mechanical properties of hybrid nanocomposites were evaluated. This study proves that the size and weight ratio of carbon-based nanofillers play a critical role in determining these properties. The optimum size and weight ratio of GnPs and MWCNTs are determined at the maximum achieved enhancement for each property. The HDPE-based nanocomposites containing GnPs with larger surface area and MWCNTs with higher aspect ratio display the highest electrical conductivity at GnPs/MWCNTs weight ratio of 2/3. The combination of GnPs with larger surface area and MWCNTs with lower aspect ratio provides the maximum Young’s modulus enhancement of hybrid nanocomposites at 1/4 weight ratio of GnPs and MWCNTs. The nanocomposite containing GnPs with the largest lateral size and MWCNTs with a higher aspect ratio at a 3/2 weight ratio exhibits the highest thermal conductivity. Also, at around the percolation threshold of GnPs, the incorporation of MWCNTs with larger aspect ratio into the HDPE-based nanocomposites containing GnPs with the largest lateral size shows a distinct synergic effect on the thermal conductivity and Young’s modulus, while an additive effect on the electrical conductivity and thermal stability.
Photomechanical actuation is preferred to electromechanical transduction because of some advantag... more Photomechanical actuation is preferred to electromechanical transduction because of some advantages including wireless connection, a producing low noise, fast response etc. However, only few materials actually exhibit photoactuation. Recently, nanotube-enriched elastomeric polymers have shown photo-actuating properties; the best results were reported for liquid crystals elastomers. In the present paper we discuss photo-actuating behavior of new photoactuating materials based on the
The effects of the aspect ratio and the addition of multiwall carbon nanotubes (MWCNTs) on the mo... more The effects of the aspect ratio and the addition of multiwall carbon nanotubes (MWCNTs) on the morphological, electrical, mechanical and thermal properties of high-density polyethylene (HDPE)-based nanocomposites are investigated. The HDPE nanocomposites with various amounts up to 18.74 wt.% of MWCNTs that have two different aspect ratios (AR), (200–400(M58) and 500–3000(M12)) were prepared by a melt mixing method, followed by compression molding. The results demonstrate that the addition of MWCNTs enhances the electrical, mechanical and thermal properties of the HDPE/MWCNTs nanocomposites. The HDPE nanocomposites with higher aspect ratio MWCNTs demonstrated a slightly better enhancement in the morphological and electrical properties than the other ones with lower aspect ratio MWCNTs. Additionally, Young's modulus and the thermal stability increased with increasing aspect ratio of MWCNTs.
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